Q:- How much time it will take to prepare this Exam?
Answer :- Depends from person to person

Q. What is the worth of this Exam?
Answer :- very valuable as it give it certify that you have gained basic and advance knowledge of Servlets and JSP.

Q. Is SCWCD is easier than SCJP?
Answer :- We can not compare two certifications.
i would say SCWCD and SCJP has altogether a different objective.
Where SCJP is more toward gaining/learning Core Java concepts , SCWCD has more inclination towards Web Development topics (like Servlet and JSP)
SCJP has more Core Java concepts (Core Java like Serialization,Generics , Fundamentals,Threading) where as SCWCD has more functional aspects of Web development like Session Management, Cookie management,HHTP protocol, JSP custom tags etc.

Thanks a lot for quick reply.......
One more thing to know...
IS sun Exam voucher is common for all exams like SCJP...?
Do you have any idea of discount price of vouchers?
From where I can buy the Exam voucher?

You can contact a NIIT center or prometric center near you. It is the best source for buying exam vouchers.
As far as discount is concerned and whether one coupon is for all exams or not, i do not know.
I am yet to buy my coupon for SCWCD exam